Index: lib/Target/X86/X86ISelLowering.cpp
===================================================================
--- lib/Target/X86/X86ISelLowering.cpp
+++ lib/Target/X86/X86ISelLowering.cpp
@@ -27842,7 +27842,9 @@
   if (InScalarVT.getSizeInBits() <= ScalarVT.getSizeInBits())
     return SDValue();
 
-  if (Subtarget.hasAVX512()) {
+  if (!Subtarget.hasSSE2())
+    return SDValue();
+  else if (Subtarget.hasAVX512()) {
     if (VT.getSizeInBits() > 512)
       return SDValue();
   } else if (Subtarget.hasAVX2()) {
Index: test/CodeGen/X86/pr27973.ll
===================================================================
--- /dev/null
+++ test/CodeGen/X86/pr27973.ll
@@ -0,0 +1,39 @@
+; REQUIRES: asserts
+; RUN: llc < %s
+
+target datalayout = "e-m:o-p:32:32-f64:32:64-f80:128-n8:16:32-S128"
+target triple = "i386-apple-macosx10.11.0"
+
+; Function Attrs: norecurse nounwind ssp
+define void @fn1() #0 {
+entry:
+  br i1 undef, label %for.body4.preheader, label %for.cond.cleanup
+
+for.body4.preheader:                              ; preds = %entry
+  br label %vector.body
+
+vector.body:                                      ; preds = %vector.body, %for.body4.preheader
+  %0 = zext <16 x i8> zeroinitializer to <16 x i32>
+  %1 = add nuw nsw <16 x i32> %0, <i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1>
+  %2 = lshr <16 x i32> %1, <i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1>
+  %3 = trunc <16 x i32> %2 to <16 x i8>
+  store <16 x i8> %3, <16 x i8>* undef, align 1, !tbaa !1, !alias.scope !4, !noalias !7
+  br label %vector.body
+
+for.cond.cleanup:                                 ; preds = %entry
+  ret void
+}
+
+attributes #0 = { norecurse nounwind ssp "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="pentium3" "target-features"="+fxsr,+mmx,+sse,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" }
+
+!llvm.ident = !{!0}
+
+!0 = !{!"clang version 3.9.0 (trunk 271435)"}
+!1 = !{!2, !2, i64 0}
+!2 = !{!"omnipotent char", !3, i64 0}
+!3 = !{!"Simple C/C++ TBAA"}
+!4 = !{!5}
+!5 = distinct !{!5, !6}
+!6 = distinct !{!6, !"LVerDomain"}
+!7 = !{!8}
+!8 = distinct !{!8, !6}